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Repair formula mangled by PR#1319 in Jan 2015

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This commit is contained in:
Richard Wackerbarth 2015-12-16 08:33:51 -06:00
parent 2932602643
commit 7c94c83765
1 changed files with 5 additions and 5 deletions
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10
Marlin/scripts/createTemperatureLookupMarlin.py
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@ -1,7 +1,7 @@
#!/usr/bin/python #!/usr/bin/python
"""Thermistor Value Lookup Table Generator """Thermistor Value Lookup Table Generator
Generates lookup to temperature values for use in a microcontroller in C format based on: Generates lookup to temperature values for use in a microcontroller in C format based on:
http://en.wikipedia.org/wiki/Steinhart-Hart_equation http://en.wikipedia.org/wiki/Steinhart-Hart_equation
The main use is for Arduino programs that read data from the circuit board described here: The main use is for Arduino programs that read data from the circuit board described here:
@ -45,7 +45,7 @@ class Thermistor:
c = (y - x) / ((l3 - l2) * (l1 + l2 + l3)) c = (y - x) / ((l3 - l2) * (l1 + l2 + l3))
b = x - c * (l1**2 + l2**2 + l1*l2) b = x - c * (l1**2 + l2**2 + l1*l2)
a = y1 - (b + l1**2 *c)*l1 a = y1 - (b + l1**2 *c)*l1
if c < 0: if c < 0:
print "//////////////////////////////////////////////////////////////////////////////////////" print "//////////////////////////////////////////////////////////////////////////////////////"
print "// WARNING: negative coefficient 'c'! Something may be wrong with the measurements! //" print "// WARNING: negative coefficient 'c'! Something may be wrong with the measurements! //"
@ -73,13 +73,13 @@ class Thermistor:
def temp(self, adc): def temp(self, adc):
"Convert ADC reading into a temperature in Celcius" "Convert ADC reading into a temperature in Celcius"
l = log(self.resist(adc)) l = log(self.resist(adc))
Tinv = self.c1 + self.c2*l + self.c3* l**3) # inverse temperature Tinv = self.c1 + self.c2*l + self.c3* l**3 # inverse temperature
return (1/Tinv) - ZERO # temperature return (1/Tinv) - ZERO # temperature
def adc(self, temp): def adc(self, temp):
"Convert temperature into a ADC reading" "Convert temperature into a ADC reading"
x = (self.c1 - (1.0 / (temp+ZERO))) / (2*self.c3) x = (self.c1 - (1.0 / (temp+ZERO))) / (2*self.c3)
y = sqrt((self.c2 / (3*self.c3)**3 + x**2) y = sqrt((self.c2 / (3*self.c3))**3 + x**2)
r = exp((y-x)**(1.0/3) - (y+x)**(1.0/3)) r = exp((y-x)**(1.0/3) - (y+x)**(1.0/3))
return (r / (self.rp + r)) * ARES return (r / (self.rp + r)) * ARES
@ -93,7 +93,7 @@ def main(argv):
r3 = 226.15 # resistance at high temperature (226.15 Ohm) r3 = 226.15 # resistance at high temperature (226.15 Ohm)
rp = 4700; # pull-up resistor (4.7 kOhm) rp = 4700; # pull-up resistor (4.7 kOhm)
num_temps = 36; # number of entries for look-up table num_temps = 36; # number of entries for look-up table
try: try:
opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="]) opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="])
except getopt.GetoptError as err: except getopt.GetoptError as err: